Forgive me for the simple question but when you pass InitialLoadSet::LoadNone to the UsdStage::Open function, does that mean that payloads are not loaded? I looked through the documentation and it wasn’t clear to me if loading prims meant payloads and not potentially something else. Are there other ways to load a prim besides payloads?
It is referring to payloads - there is no other stage-configurable “loading” mechanism, although there is also the “stage masking” feature, which can be used in combination with loading/unloading to restrict the set of prims populated on a stage.